As the micro-miniaturization of electrical and electronic circuit components has continued to reduce the size and spacing of packaged devices it has been necessary to provide increased precision interconnect structures, including those that are both flexible and robust. Typically, such structures comprise a compliant layer of patterned metal embedded in a (flexible) dielectric (ribbon) body. Opposite ends of the metal layer are either joined with or built up to an increased size and strength, and configured for attachment to electrical terminals of one or more circuit packages. Because of the wide variety of terminal connectors with which such interconnect structures may be used, the end terminals of such cables ca; be expected to have a comparable variety of shapes and sizes, which has resulted in a profusion of custom designed printed circuit interconnect structures.
One example of such a conventional (flexible) interconnect structure is described in U.S. Pat. No. 4,085,502 to Ostman et al, entitled "Jumper Cable". In accordance with the patented configuration, the thickness of a prescribed region of interconnect metal intermediate its opposite ends is selectively reduced or `sculptured` (as by milling), etched into separate tracks, and then sandwiched between a pair of flexible dielectric layers. Because the thickness of the intermediate portion of the resulting laminate structure is reduced relative to the thickness of its opposite ends, the intermediate portion is able to flex. Conversely, the thicker end portions provide rigid terminations for the respective ends of the jumper cable.
A fundamental shortcoming of the sculptured approach to the manufacture of interconnect structures is the fact that the milling or etching of the metal makes sculpturing process-intensive and limits the degree to which the intermediate portion of the metal can be `thinned`, in order to make it flexible, without creating the potential for discontinuities. Selective chemical milling of the metal can lead to undercuts at regions immediately adjacent to the thicker end mesa regions.
Unfortunately, other interconnect cable configurations and processing methodologies are either similarly complex or limit the degree to which the cable terminations can be tailored with respect to configuration, size and materials.